The exhibit is concerned with the genesis of the electrocardiographic deflection in man and dog with relation to spread of excitation from endocardium to epicardium, as determined by intramural potentials. It demonstrates the manner in which various components of the electrocardiogram develop and points out the contribution made to the genesis of the electrocardiogram by various myocardial layers. These fundamental observations explain the clinical electrocardiogram especially in coronary artery disease in a more rational light than previously possible.

DEPOLARIZATION OF THE NORMAL VENTRICLEThe classic theory of normal ventricular depolarization is illustrated diagrammatically. Depolarization is supposed to proceed at a steady, constant rate from endocardium to epicardium. Under such circumstances, a pure QS wave would occur in leads from the ventricular cavity; an R wave would occur in epicardial leads from the ventricular surface; RS waves would occur in all intramural leads between the cavity and surface. The large question